This invention relates to the preparation of alkanediols including 1,3-propanediol. In a specific aspect, the invention relates to a rhodium-catalyzed process for manufacturing 1,3-propanediol in high yields without the use of a phosphine ligand for the rhodium catalyst.
1,3-propanediol (PDO) is an intermediate in the production of polyesters for fibers and films. It is known to prepare PDO in a two-step process involving (1) the rhodium-catalyzed hydroformylation (reaction with synthesis gas, H.sub.2 /CO) of ethylene oxide to intermediate 3-hydroxypropanal (HPA) and (2) hydrogenation of the HPA to PDO. The initial hydroformylation step can be carried out at temperatures greater than 100.degree. C. and at high syngas pressures to achieve practical reaction rates. The resulting product mixture is, however, rather unselective for HPA.
In an alternate hydroformylation method, the rhodium catalyst is used in combination with a phosphine ligand to prepare HPA with greater selectivity and at lower temperature and pressure. However, the use of a phosphine ligand adds to the cost of the catalyst and increases the complexity of catalyst recycle.
It would be desirable to prepare PDO and other alkanediols in a low temperature, selective process which permitted efficient recycle of the rhodium catalyst.
It is therefore an object of the invention to provide a process for the preparation of alkanediols. In a specific embodiment, it is an object of the invention to provide an economical process for the preparation of 1,3-propanediol which does not require the use of a phosphine-ligated rhodium catalyst for preparation of the HPA intermediate.